1. Field of the Invention
The present invention relates to a method for producing an alkyl and/or cycloalkyl-substituted cyclic nitrile by the reaction of a corresponding cyclic aldehyde having a substituent such as alkyl group and cycloalkyl group with ammonia and oxygen.
2. Description of the Prior Art
Various methods have been known for the production of aromatic nitrites by the reaction of aromatic aldehydes and ammonia. For example, proposed are a method in which 20 mol of ammonia per one mole of an aromatic aldehyde is subjected to a vapor-phase catalytic reaction in the presence of a supported catalyst of copper on alumina, and then subjected to the dehydrogenation reaction into an aromatic nitrile (J. Org. Chem., 1981, 46, 754–757), a method in which an aromatic nitrile is produced by a vapor-phase catalytic reaction of an aromatic aldehyde and ammonia in the presence of a catalyst containing copper oxide and at least one of zinc oxide and chromium oxide (JP 2002-179636A), and a method in which an aromatic nitrile is produced by a vapor-phase catalytic reaction of 14 to 50 mol of ammonia per one mole of an aromatic aldehyde in the presence of molybdenum nitride (DE 19518398A). However, since a large excessive amount of ammonia should be used in these methods, the use of these methods in industrial scale involves problems of increased costs for recovery of ammonia. As another problem, it has been pointed out that the yield is reduced by the by-production of high-boiling compounds in the proposed methods (JP 2000-239247A).
If the high-boiling compounds accumulate on catalyst beds, the pressure difference of the catalyst beds increases and the catalytic activity is reduced. Therefore, the catalyst should be regenerated by removing the accumulated high-boiling compounds at regular intervals. However, it is difficult in the above methods to regenerate and reuse the catalyst by removing the high-boiling compounds accumulated on catalyst beds in a economically advantageous manner, because the copper catalyst is used in reductive atmosphere. For example, the regeneration of a deactivated catalyst by calcination in the presence of oxygen is not suitable for the above methods because the catalyst itself is oxidized.
Another method for producing the aromatic nitrile is the ammoxidation of an aromatic aldehyde in the presence of ammonia and oxygen. For example, the aromatic nitrile is produced by reacting an aromatic aldehyde with oxygen in a methanol solution containing ammonia and sodium methylate in the presence of copper chloride catalyst (Rec. Trav. Chim., 1963, 82, 757–765). However, this method requires expensive materials because the catalyst solution is highly corrosive, and increases the cost for recovering the solvent because a large amount of solvent is used.
It has been also known to produce benzonitrile by the ammoxidation of benzaldehyde in which benzaldehyde is brought into contact with ammonia and oxygen in vapor phase in the presence of a catalyst. Kogyo Kagaku Zasshi, 1964, 67, 1542–1545 teaches that the ammoxidation of benzaldehyde with ammonia and oxygen in the presence of a vanadium oxide-aluminum oxide catalyst provides benzonitrile in 85% yield. However, this document describes nothing about the reaction of an aromatic aldehyde having a substituent such as alkyl group into a corresponding aromatic nitrile.